Add potential fix for duck typing derived types

tracer/src/Datadog.Trace/DuckTyping/DuckType.Fields.cs

@@ -44,7 +44,10 @@ public static partial class DuckType
             Type returnType = targetField.FieldType;
 
             // Load the field value to the stack
-            if (UseDirectAccessTo(proxyTypeBuilder, targetType))
+            // Use targetField.DeclaringType (not targetType) to ensure IgnoresAccessChecksToAttribute
+            // is added for the assembly that actually owns the field. When targetType is a derived type
+            // in a different assembly, using targetType would miss the base type's assembly.
+            if (UseDirectAccessTo(proxyTypeBuilder, targetField.DeclaringType ?? targetType))
             {
                 // Load the instance
                 if (!targetField.IsStatic)
@@ -212,7 +215,9 @@ public static partial class DuckType
             }
 
             // We set the field value
-            if (UseDirectAccessTo(proxyTypeBuilder, targetType))
+            // Use targetField.DeclaringType (not targetType) to ensure IgnoresAccessChecksToAttribute
+            // is added for the assembly that actually owns the field.
+            if (UseDirectAccessTo(proxyTypeBuilder, targetField.DeclaringType ?? targetType))
             {
                 // If the instance and the field are public then is easy to set.
                 il.WriteTypeConversion(currentValueType, targetField.FieldType);

tracer/test/Datadog.Trace.Tests/Util/Http/HttpRequestUtilsTests.cs

@@ -199,4 +199,24 @@ public void GetUrl_ShouldFormatCorrectly(string url, bool useQueryManager, bool
         var result = HttpRequestUtils.GetUrl(uri, queryStringManager);
         result.Should().Be(expected);
     }
+
+    [Theory]
+    [InlineData("http://localhost/path", "http://localhost/path")]
+    [InlineData("https://example.com/api/users?id=123", "https://example.com/api/users")]
+    [InlineData("http://localhost:8080/test", "http://localhost:8080/test")]
+    public void GetUrl_WithDerivedUri_ShouldFormatCorrectly(string url, string expected)
+    {
+        var uri = new DerivedUri(url);
+
+        var result = HttpRequestUtils.GetUrl(uri);
+        result.Should().Be(expected);
+    }
+
+    private class DerivedUri : Uri
+    {
+        public DerivedUri(string uriString)
+            : base(uriString)
+        {
+        }
+    }
 }